Bitcoin half-life — all the time some Bitcoin private keys are lost. Over the 15 years since Bitcoin was created, it is estimated that about 30% of it is already lost. Lets say the next 20% will be lost in another 15 years, this makes half-life of Bitcoin to be 30 years.

30 years half-life is the same as for the radioactive Cesium 137 atom. It means, in 90 years only one-eight of all Bitcoin will only remain.

The game is to not lose your keys for as long as possible. Whoever is last to not lose their keys will have all the Bitcoin. Eventually everyone will lose their keys; however, long before that humans will intervene to fork the chain.